As Mary already described, newer students gets lots of feedback and encouragement. They also often get more "leading" attacks to help them *find* the correct way of applying the techniques. Over time the student starts to learn and becomes reasonably proficient. Many will see themselves as doing very well because after all, they're throwing just like the seniors, right?!?!?!? Then we start to see PBBEIPOMS. Pre Black Belt Everyone Is Picking On Me Syndrome. The more senior people start to push the techniques a bit, start to lead less and attack with more reality. Slowly but surely they're not so easy to throw because it is time for the Brown Belt to learn to do it "for reals" (tm, patent pending).

I've met many a brilliant mudansha (in their minds). Quite a few almost as brilliant shodan. Then by around nidan they start figuring out that the whole "shodan really means beginner" deal really has some foundation in reality.